[HLSL] Implement SV_GroupThreadId semantic (#117781)

lizhengxing · web-flow · commit 951a284fdff4 · 2024-12-10T13:18:49.000-08:00
Support HLSL SV_GroupThreadId attribute. For `directx` target, translate it into `dx.thread.id.in.group` in clang codeGen and lower `dx.thread.id.in.group` to `dx.op.threadIdInGroup` in LLVM DirectX backend. For `spir-v` target, translate it into `spv.thread.id.in.group` in clang codeGen and lower `spv.thread.id.in.group` to a `LocalInvocationId` builtin variable in LLVM SPIR-V backend. Fixes: #70122
diff --git a/clang/include/clang/Basic/Attr.td b/clang/include/clang/Basic/Attr.td
@@ -4651,6 +4651,13 @@ def HLSLNumThreads: InheritableAttr {
   let Documentation = [NumThreadsDocs];
 }
 
+def HLSLSV_GroupThreadID: HLSLAnnotationAttr {
+  let Spellings = [HLSLAnnotation<"SV_GroupThreadID">];
+  let Subjects = SubjectList<[ParmVar, Field]>;
+  let LangOpts = [HLSL];
+  let Documentation = [HLSLSV_GroupThreadIDDocs];
+}
+
 def HLSLSV_GroupID: HLSLAnnotationAttr {
   let Spellings = [HLSLAnnotation<"SV_GroupID">];
   let Subjects = SubjectList<[ParmVar, Field]>;
diff --git a/clang/include/clang/Basic/AttrDocs.td b/clang/include/clang/Basic/AttrDocs.td
@@ -7941,6 +7941,17 @@ randomized.
   }];
 }
 
+def HLSLSV_GroupThreadIDDocs : Documentation {
+  let Category = DocCatFunction;
+  let Content = [{
+The ``SV_GroupThreadID`` semantic, when applied to an input parameter, specifies which
+individual thread within a thread group is executing in. This attribute is
+only supported in compute shaders.
+
+The full documentation is available here: https://docs.microsoft.com/en-us/windows/win32/direct3dhlsl/sv-groupthreadid
+  }];
+}
+
 def HLSLSV_GroupIDDocs : Documentation {
   let Category = DocCatFunction;
   let Content = [{
diff --git a/clang/include/clang/Sema/SemaHLSL.h b/clang/include/clang/Sema/SemaHLSL.h
@@ -119,6 +119,7 @@ class SemaHLSL : public SemaBase {
   void handleNumThreadsAttr(Decl *D, const ParsedAttr &AL);
   void handleWaveSizeAttr(Decl *D, const ParsedAttr &AL);
   void handleSV_DispatchThreadIDAttr(Decl *D, const ParsedAttr &AL);
+  void handleSV_GroupThreadIDAttr(Decl *D, const ParsedAttr &AL);
   void handleSV_GroupIDAttr(Decl *D, const ParsedAttr &AL);
   void handlePackOffsetAttr(Decl *D, const ParsedAttr &AL);
   void handleShaderAttr(Decl *D, const ParsedAttr &AL);
diff --git a/clang/lib/CodeGen/CGHLSLRuntime.cpp b/clang/lib/CodeGen/CGHLSLRuntime.cpp
@@ -389,6 +389,11 @@ llvm::Value *CGHLSLRuntime::emitInputSemantic(IRBuilder<> &B,
         CGM.getIntrinsic(getThreadIdIntrinsic());
     return buildVectorInput(B, ThreadIDIntrinsic, Ty);
   }
+  if (D.hasAttr<HLSLSV_GroupThreadIDAttr>()) {
+    llvm::Function *GroupThreadIDIntrinsic =
+        CGM.getIntrinsic(getGroupThreadIdIntrinsic());
+    return buildVectorInput(B, GroupThreadIDIntrinsic, Ty);
+  }
   if (D.hasAttr<HLSLSV_GroupIDAttr>()) {
     llvm::Function *GroupIDIntrinsic = CGM.getIntrinsic(Intrinsic::dx_group_id);
     return buildVectorInput(B, GroupIDIntrinsic, Ty);
diff --git a/clang/lib/CodeGen/CGHLSLRuntime.h b/clang/lib/CodeGen/CGHLSLRuntime.h
@@ -86,6 +86,7 @@ class CGHLSLRuntime {
   GENERATE_HLSL_INTRINSIC_FUNCTION(Step, step)
   GENERATE_HLSL_INTRINSIC_FUNCTION(Radians, radians)
   GENERATE_HLSL_INTRINSIC_FUNCTION(ThreadId, thread_id)
+  GENERATE_HLSL_INTRINSIC_FUNCTION(GroupThreadId, thread_id_in_group)
   GENERATE_HLSL_INTRINSIC_FUNCTION(FDot, fdot)
   GENERATE_HLSL_INTRINSIC_FUNCTION(SDot, sdot)
   GENERATE_HLSL_INTRINSIC_FUNCTION(UDot, udot)
diff --git a/clang/lib/Parse/ParseHLSL.cpp b/clang/lib/Parse/ParseHLSL.cpp
@@ -280,6 +280,7 @@ void Parser::ParseHLSLAnnotations(ParsedAttributes &Attrs,
   case ParsedAttr::UnknownAttribute:
     Diag(Loc, diag::err_unknown_hlsl_semantic) << II;
     return;
+  case ParsedAttr::AT_HLSLSV_GroupThreadID:
   case ParsedAttr::AT_HLSLSV_GroupID:
   case ParsedAttr::AT_HLSLSV_GroupIndex:
   case ParsedAttr::AT_HLSLSV_DispatchThreadID:
diff --git a/clang/lib/Sema/SemaDeclAttr.cpp b/clang/lib/Sema/SemaDeclAttr.cpp
@@ -7114,6 +7114,9 @@ ProcessDeclAttribute(Sema &S, Scope *scope, Decl *D, const ParsedAttr &AL,
   case ParsedAttr::AT_HLSLWaveSize:
     S.HLSL().handleWaveSizeAttr(D, AL);
     break;
+  case ParsedAttr::AT_HLSLSV_GroupThreadID:
+    S.HLSL().handleSV_GroupThreadIDAttr(D, AL);
+    break;
   case ParsedAttr::AT_HLSLSV_GroupID:
     S.HLSL().handleSV_GroupIDAttr(D, AL);
     break;
diff --git a/clang/lib/Sema/SemaHLSL.cpp b/clang/lib/Sema/SemaHLSL.cpp
@@ -434,6 +434,7 @@ void SemaHLSL::CheckSemanticAnnotation(
   switch (AnnotationAttr->getKind()) {
   case attr::HLSLSV_DispatchThreadID:
   case attr::HLSLSV_GroupIndex:
+  case attr::HLSLSV_GroupThreadID:
   case attr::HLSLSV_GroupID:
     if (ST == llvm::Triple::Compute)
       return;
@@ -787,6 +788,15 @@ void SemaHLSL::handleSV_DispatchThreadIDAttr(Decl *D, const ParsedAttr &AL) {
                  HLSLSV_DispatchThreadIDAttr(getASTContext(), AL));
 }
 
+void SemaHLSL::handleSV_GroupThreadIDAttr(Decl *D, const ParsedAttr &AL) {
+  auto *VD = cast<ValueDecl>(D);
+  if (!diagnoseInputIDType(VD->getType(), AL))
+    return;
+
+  D->addAttr(::new (getASTContext())
+                 HLSLSV_GroupThreadIDAttr(getASTContext(), AL));
+}
+
 void SemaHLSL::handleSV_GroupIDAttr(Decl *D, const ParsedAttr &AL) {
   auto *VD = cast<ValueDecl>(D);
   if (!diagnoseInputIDType(VD->getType(), AL))
diff --git a/clang/test/CodeGenHLSL/semantics/SV_GroupThreadID.hlsl b/clang/test/CodeGenHLSL/semantics/SV_GroupThreadID.hlsl
@@ -0,0 +1,36 @@
+// RUN: %clang_cc1 -triple dxil-pc-shadermodel6.3-library -x hlsl -emit-llvm -finclude-default-header -disable-llvm-passes -o - %s | FileCheck %s --check-prefixes=CHECK,CHECK-DXIL -DTARGET=dx
+// RUN: %clang_cc1 -triple spirv-linux-vulkan-library -x hlsl -emit-llvm -finclude-default-header -disable-llvm-passes -o - %s | FileCheck %s --check-prefixes=CHECK,CHECK-SPIRV -DTARGET=spv
+
+// Make sure SV_GroupThreadID translated into dx.thread.id.in.group for directx target and spv.thread.id.in.group for spirv target.
+
+// CHECK:       define void @foo()
+// CHECK:       %[[#ID:]] = call i32 @llvm.[[TARGET]].thread.id.in.group(i32 0)
+// CHECK-DXIL:       call void @{{.*}}foo{{.*}}(i32 %[[#ID]])
+// CHECK-SPIRV:      call spir_func void @{{.*}}foo{{.*}}(i32 %[[#ID]])
+[shader("compute")]
+[numthreads(8,8,1)]
+void foo(uint Idx : SV_GroupThreadID) {}
+
+// CHECK:       define void @bar()
+// CHECK:       %[[#ID_X:]] = call i32 @llvm.[[TARGET]].thread.id.in.group(i32 0)
+// CHECK:       %[[#ID_X_:]] = insertelement <2 x i32> poison, i32 %[[#ID_X]], i64 0
+// CHECK:       %[[#ID_Y:]] = call i32 @llvm.[[TARGET]].thread.id.in.group(i32 1)
+// CHECK:       %[[#ID_XY:]] = insertelement <2 x i32> %[[#ID_X_]], i32 %[[#ID_Y]], i64 1
+// CHECK-DXIL:  call void @{{.*}}bar{{.*}}(<2 x i32> %[[#ID_XY]])
+// CHECK-SPIRV:  call spir_func void @{{.*}}bar{{.*}}(<2 x i32> %[[#ID_XY]])
+[shader("compute")]
+[numthreads(8,8,1)]
+void bar(uint2 Idx : SV_GroupThreadID) {}
+
+// CHECK:  define void @test()
+// CHECK:  %[[#ID_X:]] = call i32 @llvm.[[TARGET]].thread.id.in.group(i32 0)
+// CHECK:  %[[#ID_X_:]] = insertelement <3 x i32> poison, i32 %[[#ID_X]], i64 0
+// CHECK:  %[[#ID_Y:]] = call i32 @llvm.[[TARGET]].thread.id.in.group(i32 1)
+// CHECK:  %[[#ID_XY:]] = insertelement <3 x i32> %[[#ID_X_]], i32 %[[#ID_Y]], i64 1
+// CHECK:  %[[#ID_Z:]] = call i32 @llvm.[[TARGET]].thread.id.in.group(i32 2)
+// CHECK:  %[[#ID_XYZ:]] = insertelement <3 x i32> %[[#ID_XY]], i32 %[[#ID_Z]], i64 2
+// CHECK-DXIL:   call void @{{.*}}test{{.*}}(<3 x i32> %[[#ID_XYZ]])
+// CHECK-SPIRV:  call spir_func void @{{.*}}test{{.*}}(<3 x i32> %[[#ID_XYZ]])
+[shader("compute")]
+[numthreads(8,8,1)]
+void test(uint3 Idx : SV_GroupThreadID) {}
diff --git a/clang/test/SemaHLSL/Semantics/entry_parameter.hlsl b/clang/test/SemaHLSL/Semantics/entry_parameter.hlsl
@@ -1,16 +1,14 @@
 // RUN: %clang_cc1 -triple dxil-pc-shadermodel6.0-compute -hlsl-entry CSMain -x hlsl  -finclude-default-header  -ast-dump -o - %s | FileCheck %s
-// RUN: %clang_cc1 -triple dxil-pc-shadermodel6.0-mesh -hlsl-entry CSMain -x hlsl -finclude-default-header  -verify -o - %s
 
 [numthreads(8,8,1)]
-// expected-error@+3 {{attribute 'SV_GroupIndex' is unsupported in 'mesh' shaders, requires compute}}
-// expected-error@+2 {{attribute 'SV_DispatchThreadID' is unsupported in 'mesh' shaders, requires compute}}
-// expected-error@+1 {{attribute 'SV_GroupID' is unsupported in 'mesh' shaders, requires compute}}
-void CSMain(int GI : SV_GroupIndex, uint ID : SV_DispatchThreadID, uint GID : SV_GroupID) {
-// CHECK: FunctionDecl 0x{{[0-9a-fA-F]+}} <{{.*}}> line:[[@LINE-1]]:6 CSMain 'void (int, uint, uint)'
+void CSMain(int GI : SV_GroupIndex, uint ID : SV_DispatchThreadID, uint GID : SV_GroupID, uint GThreadID : SV_GroupThreadID) {
+// CHECK: FunctionDecl 0x{{[0-9a-fA-F]+}} <{{.*}}> line:[[@LINE-1]]:6 CSMain 'void (int, uint, uint, uint)'
 // CHECK-NEXT: ParmVarDecl 0x{{[0-9a-fA-F]+}} <{{.*}}> col:17 GI 'int'
 // CHECK-NEXT: HLSLSV_GroupIndexAttr
 // CHECK-NEXT: ParmVarDecl 0x{{[0-9a-fA-F]+}} <{{.*}}> col:42 ID 'uint'
 // CHECK-NEXT: HLSLSV_DispatchThreadIDAttr
 // CHECK-NEXT: ParmVarDecl 0x{{[0-9a-fA-F]+}} <{{.*}}> col:73 GID 'uint'
 // CHECK-NEXT: HLSLSV_GroupIDAttr
+// CHECK-NEXT: ParmVarDecl 0x{{[0-9a-fA-F]+}} <{{.*}}> col:96 GThreadID 'uint'
+// CHECK-NEXT: HLSLSV_GroupThreadIDAttr
 }
diff --git a/clang/test/SemaHLSL/Semantics/invalid_entry_parameter.hlsl b/clang/test/SemaHLSL/Semantics/invalid_entry_parameter.hlsl
@@ -49,3 +49,33 @@ struct ST2_GID {
     static uint GID : SV_GroupID;
     uint s_gid : SV_GroupID;
 };
+
+[numthreads(8,8,1)]
+// expected-error@+1 {{attribute 'SV_GroupThreadID' only applies to a field or parameter of type 'uint/uint2/uint3'}}
+void CSMain_GThreadID(float ID : SV_GroupThreadID) {
+}
+
+[numthreads(8,8,1)]
+// expected-error@+1 {{attribute 'SV_GroupThreadID' only applies to a field or parameter of type 'uint/uint2/uint3'}}
+void CSMain2_GThreadID(ST GID : SV_GroupThreadID) {
+
+}
+
+void foo_GThreadID() {
+// expected-warning@+1 {{'SV_GroupThreadID' attribute only applies to parameters and non-static data members}}
+  uint GThreadIS : SV_GroupThreadID;
+}
+
+struct ST2_GThreadID {
+// expected-warning@+1 {{'SV_GroupThreadID' attribute only applies to parameters and non-static data members}}
+    static uint GThreadID : SV_GroupThreadID;
+    uint s_gthreadid : SV_GroupThreadID;
+};
+
+
+[shader("vertex")]
+// expected-error@+4 {{attribute 'SV_GroupIndex' is unsupported in 'vertex' shaders, requires compute}}
+// expected-error@+3 {{attribute 'SV_DispatchThreadID' is unsupported in 'vertex' shaders, requires compute}}
+// expected-error@+2 {{attribute 'SV_GroupID' is unsupported in 'vertex' shaders, requires compute}}
+// expected-error@+1 {{attribute 'SV_GroupThreadID' is unsupported in 'vertex' shaders, requires compute}}
+void vs_main(int GI : SV_GroupIndex, uint ID : SV_DispatchThreadID, uint GID : SV_GroupID, uint GThreadID : SV_GroupThreadID) {}
diff --git a/clang/test/SemaHLSL/Semantics/valid_entry_parameter.hlsl b/clang/test/SemaHLSL/Semantics/valid_entry_parameter.hlsl
@@ -49,3 +49,28 @@ void CSMain3_GID(uint3 : SV_GroupID) {
 // CHECK-NEXT: ParmVarDecl 0x{{[0-9a-fA-F]+}} <{{.*}}> col:24 'uint3'
 // CHECK-NEXT: HLSLSV_GroupIDAttr
 }
+
+[numthreads(8,8,1)]
+void CSMain_GThreadID(uint ID : SV_GroupThreadID) {
+// CHECK: FunctionDecl 0x{{[0-9a-fA-F]+}} <{{.*}}> line:[[@LINE-1]]:6 CSMain_GThreadID 'void (uint)'
+// CHECK-NEXT: ParmVarDecl 0x{{[0-9a-fA-F]+}} <{{.*}}> col:28 ID 'uint'
+// CHECK-NEXT: HLSLSV_GroupThreadIDAttr
+}
+[numthreads(8,8,1)]
+void CSMain1_GThreadID(uint2 ID : SV_GroupThreadID) {
+// CHECK: FunctionDecl 0x{{[0-9a-fA-F]+}} <{{.*}}> line:[[@LINE-1]]:6 CSMain1_GThreadID 'void (uint2)'
+// CHECK-NEXT: ParmVarDecl 0x{{[0-9a-fA-F]+}} <{{.*}}> col:30 ID 'uint2'
+// CHECK-NEXT: HLSLSV_GroupThreadIDAttr
+}
+[numthreads(8,8,1)]
+void CSMain2_GThreadID(uint3 ID : SV_GroupThreadID) {
+// CHECK: FunctionDecl 0x{{[0-9a-fA-F]+}} <{{.*}}> line:[[@LINE-1]]:6 CSMain2_GThreadID 'void (uint3)'
+// CHECK-NEXT: ParmVarDecl 0x{{[0-9a-fA-F]+}} <{{.*}}> col:30 ID 'uint3'
+// CHECK-NEXT: HLSLSV_GroupThreadIDAttr
+}
+[numthreads(8,8,1)]
+void CSMain3_GThreadID(uint3 : SV_GroupThreadID) {
+// CHECK: FunctionDecl 0x{{[0-9a-fA-F]+}} <{{.*}}> line:[[@LINE-1]]:6 CSMain3_GThreadID 'void (uint3)'
+// CHECK-NEXT: ParmVarDecl 0x{{[0-9a-fA-F]+}} <{{.*}}> col:30 'uint3'
+// CHECK-NEXT: HLSLSV_GroupThreadIDAttr
+}
diff --git a/llvm/include/llvm/IR/IntrinsicsSPIRV.td b/llvm/include/llvm/IR/IntrinsicsSPIRV.td
@@ -59,6 +59,7 @@ let TargetPrefix = "spv" in {
 
   // The following intrinsic(s) are mirrored from IntrinsicsDirectX.td for HLSL support.
   def int_spv_thread_id : Intrinsic<[llvm_i32_ty], [llvm_i32_ty], [IntrNoMem, IntrWillReturn]>;
+  def int_spv_thread_id_in_group : Intrinsic<[llvm_i32_ty], [llvm_i32_ty], [IntrNoMem, IntrWillReturn]>;
   def int_spv_all : DefaultAttrsIntrinsic<[llvm_i1_ty], [llvm_any_ty], [IntrNoMem]>;
   def int_spv_any : DefaultAttrsIntrinsic<[llvm_i1_ty], [llvm_any_ty], [IntrNoMem]>;
   def int_spv_cross : DefaultAttrsIntrinsic<[llvm_anyfloat_ty], [LLVMMatchType<0>, LLVMMatchType<0>], [IntrNoMem]>;
diff --git a/llvm/lib/Target/SPIRV/SPIRVInstructionSelector.cpp b/llvm/lib/Target/SPIRV/SPIRVInstructionSelector.cpp
@@ -262,9 +262,6 @@ class SPIRVInstructionSelector : public InstructionSelector {
   bool selectSaturate(Register ResVReg, const SPIRVType *ResType,
                       MachineInstr &I) const;
 
-  bool selectSpvThreadId(Register ResVReg, const SPIRVType *ResType,
-                         MachineInstr &I) const;
-
   bool selectWaveOpInst(Register ResVReg, const SPIRVType *ResType,
                         MachineInstr &I, unsigned Opcode) const;
 
@@ -310,6 +307,9 @@ class SPIRVInstructionSelector : public InstructionSelector {
   void extractSubvector(Register &ResVReg, const SPIRVType *ResType,
                         Register &ReadReg, MachineInstr &InsertionPoint) const;
   bool BuildCOPY(Register DestReg, Register SrcReg, MachineInstr &I) const;
+  bool loadVec3BuiltinInputID(SPIRV::BuiltIn::BuiltIn BuiltInValue,
+                              Register ResVReg, const SPIRVType *ResType,
+                              MachineInstr &I) const;
 };
 
 } // end anonymous namespace
@@ -2825,7 +2825,21 @@ bool SPIRVInstructionSelector::selectIntrinsic(Register ResVReg,
       return BuildCOPY(ResVReg, I.getOperand(2).getReg(), I);
     break;
   case Intrinsic::spv_thread_id:
-    return selectSpvThreadId(ResVReg, ResType, I);
+    // The HLSL SV_DispatchThreadID semantic is lowered to llvm.spv.thread.id
+    // intrinsic in LLVM IR for SPIR-V backend.
+    //
+    // In SPIR-V backend, llvm.spv.thread.id is now correctly translated to a
+    // `GlobalInvocationId` builtin variable
+    return loadVec3BuiltinInputID(SPIRV::BuiltIn::GlobalInvocationId, ResVReg,
+                                  ResType, I);
+  case Intrinsic::spv_thread_id_in_group:
+    // The HLSL SV_GroupThreadId semantic is lowered to
+    // llvm.spv.thread.id.in.group intrinsic in LLVM IR for SPIR-V backend.
+    //
+    // In SPIR-V backend, llvm.spv.thread.id.in.group is now correctly
+    // translated to a `LocalInvocationId` builtin variable
+    return loadVec3BuiltinInputID(SPIRV::BuiltIn::LocalInvocationId, ResVReg,
+                                  ResType, I);
   case Intrinsic::spv_fdot:
     return selectFloatDot(ResVReg, ResType, I);
   case Intrinsic::spv_udot:
@@ -3525,30 +3539,29 @@ bool SPIRVInstructionSelector::selectLog10(Register ResVReg,
                        .constrainAllUses(TII, TRI, RBI);
 }
 
-bool SPIRVInstructionSelector::selectSpvThreadId(Register ResVReg,
-                                                 const SPIRVType *ResType,
-                                                 MachineInstr &I) const {
-  // DX intrinsic: @llvm.dx.thread.id(i32)
-  // ID  Name      Description
-  // 93  ThreadId  reads the thread ID
-
+// Generate the instructions to load 3-element vector builtin input
+// IDs/Indices.
+// Like: GlobalInvocationId, LocalInvocationId, etc....
+bool SPIRVInstructionSelector::loadVec3BuiltinInputID(
+    SPIRV::BuiltIn::BuiltIn BuiltInValue, Register ResVReg,
+    const SPIRVType *ResType, MachineInstr &I) const {
   MachineIRBuilder MIRBuilder(I);
   const SPIRVType *U32Type = GR.getOrCreateSPIRVIntegerType(32, MIRBuilder);
   const SPIRVType *Vec3Ty =
       GR.getOrCreateSPIRVVectorType(U32Type, 3, MIRBuilder);
   const SPIRVType *PtrType = GR.getOrCreateSPIRVPointerType(
       Vec3Ty, MIRBuilder, SPIRV::StorageClass::Input);
 
-  // Create new register for GlobalInvocationID builtin variable.
+  // Create new register for the input ID builtin variable.
   Register NewRegister =
       MIRBuilder.getMRI()->createVirtualRegister(&SPIRV::iIDRegClass);
   MIRBuilder.getMRI()->setType(NewRegister, LLT::pointer(0, 64));
   GR.assignSPIRVTypeToVReg(PtrType, NewRegister, MIRBuilder.getMF());
 
-  // Build GlobalInvocationID global variable with the necessary decorations.
+  // Build global variable with the necessary decorations for the input ID
+  // builtin variable.
   Register Variable = GR.buildGlobalVariable(
-      NewRegister, PtrType,
-      getLinkStringForBuiltIn(SPIRV::BuiltIn::GlobalInvocationId), nullptr,
+      NewRegister, PtrType, getLinkStringForBuiltIn(BuiltInValue), nullptr,
       SPIRV::StorageClass::Input, nullptr, true, true,
       SPIRV::LinkageType::Import, MIRBuilder, false);
 
@@ -3565,12 +3578,12 @@ bool SPIRVInstructionSelector::selectSpvThreadId(Register ResVReg,
           .addUse(GR.getSPIRVTypeID(Vec3Ty))
           .addUse(Variable);
 
-  // Get Thread ID index. Expecting operand is a constant immediate value,
+  // Get the input ID index. Expecting operand is a constant immediate value,
   // wrapped in a type assignment.
   assert(I.getOperand(2).isReg());
   const uint32_t ThreadId = foldImm(I.getOperand(2), MRI);
 
-  // Extract the thread ID from the loaded vector value.
+  // Extract the input ID from the loaded vector value.
   MachineBasicBlock &BB = *I.getParent();
   auto MIB = BuildMI(BB, I, I.getDebugLoc(), TII.get(SPIRV::OpCompositeExtract))
                  .addDef(ResVReg)
diff --git a/llvm/test/CodeGen/SPIRV/hlsl-intrinsics/SV_GroupThreadID.ll b/llvm/test/CodeGen/SPIRV/hlsl-intrinsics/SV_GroupThreadID.ll
